Technical data

BACnet/IP Controller 750-830 • 99
Programming the PFC Using WAGO-I/O-PRO CAA
WAGO-I/O-SYSTEM 750
BACnet/IP Controller
3.1.8.4 General Information about IEC Tasks
Note
Please note the following information when programming your IEC tasks.
• IEC tasks must have different priorities, as otherwise an error will occur
during translating of the application program.
• An ongoing task may be interrupted by tasks with higher priorities. Execu-
tion of the task that has been interrupted is resumed only when there are no
other higher-priority tasks to be executed.
• If several IEC tasks utilize input or output variables with the same, or over-
lapping addresses in the process image, the values for the input or output
variables may change while the IEC task is being executed!
• Running tasks are halted after each task cycle for a duration that is half the
time that the task requires (minimum 1 ms). Execution of the task is then
resumed.
Example: 1st Task 4 ms ! Waiting period 2 ms
2nd Task 2 ms ! Waiting period 1 ms
• If no task is incorporated in the task configuration, a freely running default
task is created internally during the translation. The watchdog for this task
is deactivated. This task, called "Default task," is recognized by this name
in the firmware, meaning that the name "Default task" cannot be used for
other task names.
• Sensitivity is of significance only for cyclic tasks. The values 1 and 0 are
equivalent with regard to sensitivity. A sensitivity value of 0 or 1 results in
the watchdog event being triggered when the watchdog time is exceeded
on time. With a sensitivity value of 2, for instance, the watchdog time must
be exceeded in two consecutive task cycles in order for the watchdog
event to be triggered.
• The following applies to cyclic tasks with watchdog activated:
If the set, maximum runtime is less than or equal to the call interval, a vio-
lation of the call interval likewise results in the watchdog event being trig-
gered, regardless of the value set for sensitivity.
• If the set runtime is greater than the call interval the watchdog event is trig-
gered when the maximum runtime is reached, regardless of the value set
for sensitivity.